1. Technical Field
The present disclosure relates to an integrated control circuit for a switch of a current path with a leading-edge blanking device of the current signal.
2. Description of the Related Art
In switching converters and other circuits employing switching power transistors, the operation of the circuit often depends on the current flowing through said transistors.
For example, in switching converters using the control mode referred to as “peak current mode” or “current programming mode”, the turn-on of the power transistor is controlled by a clock signal (for example, generated by a local oscillator or related to a particular event in the power circuit), while the turn-off is determined by the current flowing through said transistor reaching a threshold level. Furthermore, most switching converters have protection circuits that turn off the power transistor if the current through the transistor is excessive, to avoid damage to the converter. For example, FIG. 1 shows the block circuit scheme of a typical, commercially available integrated control circuit of the peak current mode type, included in a typical converter. Example waveforms of the control circuit of FIG. 1 are shown in FIG. 2. The integrated control circuit 1 is adapted to control the gate terminal of a transistor MOS M1 where a current Ip flows. The integrated control circuit 1 receives the current signal If generated by the feedback block 2. The current If is a function of the output voltage Vout. The current If is sunk from an input of the integrated control circuit 1, resulting in the generation of the error signal Ve. The error signal Ve is applied to the inverting terminal of the PWM comparator 4 having, on the non-inverting input, the voltage Vcs developed by the current Ip across the resistance Rs, connected between the source of transistor M1 and ground GND. The output of comparator 4 is the reset input R of the PWM latch 5 having, on a set input S, a clock signal CLOCK. The output Q of the PWM latch is connected to the input of a driver 6 that drives the gate terminal of transistor M1 with the signal G. Vdrain is the voltage between the drain terminal of transistor M1 and ground GND; Is is the current flowing on the secondary side of the transformer T, whereas the current Ip flowing through M1 flows through the transformer primary side.
The resistor Rs placed between the source terminal of M1 and ground GND converts the level of said current Ip into a voltage signal Vcs that is provided to the control and/or protection circuits in FIG. 1.